The present invention relates to an automatic control valve with an isolation valve, and particularly relates to a valve able to isolate a pilot valve which may be controlled manually or by automatic piloting.
The present invention relates further to a pressure control valve which combines a damping throttle valve with a manual adjusting valve.
Various automatic control valves are extensively used in industry and may be classified as general purpose valves, hydropneumatic valves and instrument valves according to their field of usage. They can make use of various power sources, including the energy of the medium itself for actuating the valve, to meet demands for pressure, flow and direction. However, failure or abnormal operation of any automatic valve will result from changes in external conditions. For example, electric power cutoff, overvoltage or under voltage, or excessively high or low pipeline pressure will cause magnetic valves to fail. For an automatic valve in the field of general purpose valves and instrument valves, the conventional method for solving the aforementioned problems is to mount an automatic control valve using a by-pass isolation method. A by-pass isolation method is shown in FIG. 10 of the accompanying drawings, wherein (91) is an automatic control valve, (92) is a by-pass manual valve, (93) and (94) are isolation manual valves. Such a pipeline can be controlled manually and repaired on-line when the automatic control valve is out of order. The so-called on-line repair guarantees that the whole system will work without interruption while the automatic control valve is opened or dismantled for repair. This method is utilized at the expense of occupying more space and an increase of cost. When using an automatic control valve in a hydropneumatic system where space is limited, such a method is generally not used and repair has to be done by shutting down the entire system.
The automatic control valves used in industry are mostly of a pilot type which have the distinct advantage in using a smaller pilot valve to control a larger main valve, so as to decrease volume, reduce weight and lower consumption and cost. However, this kind of pilot type automatic control valve often suffers failures at the pilot valve side. In view of such an analysis, U.S. Pat. No. 4,816,083 entitled "Multifunctional Electromagnetic Valve Assembly", has put forward a new concept that two crews are used to isolate the pilot valve which makes on-line repair possible and thus is well received in engineering circles. However, such a structure is not the simplest, and manual operation is not yet convenient. And, this concept is limited to the field of magnetic valves.
On the other hand, existing automatic control valves in hydropneumatic system have a built-in manual pressure adjusting valve, a damping throttle valve and a pressure compensating throttle valve which are disposed separately, resulting in numerous parts, bulky volume and high cost and thus improvements are needed.